Samenvatting:In the framework of the project 'Investigation of blade tip modificationsfor acoustic and rotor performance improvement' experimental research is
performed on the UNIWEX wind turbine in Schnittlingen, Germany. The task of
ECN in the coordinated project is the performance and evaluation of the
acoustic measurements. This document addresses the acoustic measurements
only. Experiments have been performed with different combinations of the
blade tip plan forms (reference, shark and ogee), blade tip edges (round and
beveled) and trailing edges (sharp and beveled). The experimental blade tips
have been mounted on one of the UNIWEX blades and the other blade remained
unchanged. Although the contribution of the hydraulic noise to the total
noise level is very high, the use of an acoustical parabola made it possible
to quantify the differences in the noise production of the various blade tips
for frequencies between 800 Hz and 5 kHz. The results of the measurements
will be assessed by all members of the project group. The conclusions based
upon the results presented in this report will be formulated in the final
project report. 6 figs., 1 tab., 5 refs.